U-shaped and not longitudinally split; two centrosomes present (c).
The centrosomes with their astral figures have been formed, and have taken their places near each pole of the nucleus.
Each of the two centrosomes appears to send out from itself delicate radiating fibres into the surrounding cell substance (Fig.
Each half of each chromosome separates from its fellow, and moves to the opposite end of the nucleus toward the two centrosomes (Fig.
The centrosomes are separate and the equatorial plate of chromosomes, cr, is between them.
Whether they are pulled apart or pushed apart by the spindle fibres is not certain, although it is apparently sure that these fibres from the centrosomes are engaged in the matter.
In this division, in some cases at least, the spindle fibres bear a part--a fact which again points to the importance of the centrosomes and the forces which radiate from them.
These radiating fibres, whether arising from the centrosomes or not, certainly all centre in these bodies, a fact which indicates that the centrosomes contain the forces which regulate their appearance.
The centrosomes are separating but are connected by fibres.
Moreover, the various fibres which surround the centrosomes in cell division and whose contractions and expansions, as we have seen, pull the chromosomes apart in cell division, are parts of the cell substance.
The centrosomes have divided preparatory to the next division, and the cell is beginning to divide.
These two asters and the centrosomes within them have been spoken of as the dynamic centre of the cell since they appear to control the forces which lead to cell division.
The final stage is that of two artificial cells in juxtaposition, whose nuclei are formed by the original centrosomes augmented by the chromatin bands or chromosomes (Fig.
In the preparation one may see the distance between the two poles slowly increase, the poles gradually separating from one another just as do the centrosomes of an ovum during karyokinesis.
In nature these two centres of positive concentration are introduced into the protoplasm of the cell by fecundation--that is, by the entrance of the centrosomes of the sperm cell.
The daughter centrosomesseparate from one another, travelling to opposite poles of the nucleus.
Meves, however, maintains the possibility that the numerous centrosomes appearing in the egg arise by the rapid fragmentation of a centrosome already present.
Hermann, is visible from the very first separation of the daughter centrosomes (e.
Not only may the sperm centrosomes totally disappear before reaching the egg-nucleus, but in the latter type the definitive centrosomes appear while the last traces of the sperm asters are still visible.
Fol (1873) regarded the centrosomes as centres of attractive forces, and compared the mitotic figure to the lines of force in the magnetic field, a comparison made by numerous subsequent workers.
At the same time the two centrosomes separate from each other on each side of the nucleus.
Figures 3 and 4 show that, while these changes are being produced, each of the two centrosomes is surrounded by stellate rays.
Directly afterwards the chromosomes arrange themselves regularly in line, like soldiers at drill, following one of the larger diameters of the cell, and forming a barrier between the two centrosomes (Fig.
Plate I, and divide longitudinally into two halves which are then attracted in opposite directions by the rays of each of the centrosomes (Fig.
If, in a froth of the same kind, the air is extracted from an alveolus, a cone of attraction is seen to form, like those about the centrosomes which result in the division of the nucleus.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "centrosomes" in a variety of sentences. We hope that you will now be able to make sentences using this word.
